Pushbutton reset undervoltage release device

ABSTRACT

An electric circuit breaker is provided with an undervoltage release having a manual reset button independent of the handle used for manually opening and closing the circuits controlled by the circuit breaker. The undervoltage release device includes a solenoid plunger movable between a seated position and a released position and a tripping member movable into and out of a tripping position in response to the movement of the plunger. The reset button operates on an actuator lever operatively associated with the separate tripping member and plunger so that upon actuation of the button the tripping member is urged toward a tripping position and the plunger is urged toward the seated position.

United States Patent Powell [451 Apr. 23, 1974 PUSHBUTTON RESETUNDERVOLTAGE RELEASE DEVICE David B. Powell, Bristol, Conn.

General Electric Company, New York, N.Y.

Filed: July 5, 1973 Appl. No.: 376,459

Inventor:

Assignee:

US. Cl. 335/20, 335/166 Int. Cl. H0lh 83/12 Field of Search 335/20, 27,26, 166

References Cited UNITED STATES PATENTS 9/1966 Franz 335/166 12/1966Kiesel et a1. 335/20 6/1969 Murphy, Jr. et al. 335/166 PrimaryExaminerl-larold Broome Attorney, Agent, or FirmRobert A. Cahill; PhilipL. Schlamp; Frank L. Neuhauser [57] ABSTRACT An electric circuit breakeris provided with an undervoltage release having a manual reset buttonindependent of the handle used for manually opening and closing thecircuits controlled by the circuit breaker.

The undervoltage release device includes a solenoid plunger movablebetween a seated position and a released position and a tripping membermovable into and out of a tripping position in response to the movementof the plunger. The reset button operates on an actuator leveroperatively associated with the separate tripping member and plunger sothat upon' actuation of the button the tripping member is urged .towarda tripping position and the plunger is urged toward the seated position.

15 Claims, 6 Drawing Figures PATENTEDAPR 23 m4 3,806; 846 m 1 [IF 2 FIG.

PUSI-IBUTTON RESET UNDERVOLTAGE RELEASE DEVICE BACKGROUND AND SUMMARY OFTHE INVENTION The present invention relates generally to electriccircuit breakers. More particularly is is concerned with a new andimproved electric circuit breaker having an undervoltage release typedevice responsive to a decrease in line voltage within a circuitcontrolled by the breaker.

Undervoltage release type devices utilized heretofore have commonlyemployed a solenoid retained actuator or plunger that is held by thesolenoid during normal operation and is released in response to apredetermined drop in the line voltage. Typically the plunger isreseated or reset by the opening or tripping movement of some part ofthe breaker mechanism. As a result a common problem has existed withundervoltage release devices; namely, the reversal of this trippingmotion or a release of the reseated plunger must take place before theundervoltage release device can trip the breaker latch. Consequently, ifan undervoltage condition persists and the circuit breaker is moved toits ON position, a race occurs between latch release by the undervoltagerelease device and movement of the contacts toward their closed circuitpositions. This becomes particularly critical in mining useapplications. Under such use it is extremely important for safetyreasons that there be no re-energization of the cable which originallysignaled the undervoltage release device until that cable has beenrepaired.

Although many different approaches have been used in solving thisproblem, none has been completely satisfactory. According to oneapproach, a fine adjustment of the mechanism makes it possible to causelatch release and therefore tripping early enough to prevent thecontacts from re-energizing the line. However, such an adjustment puts aheavy strain on the mechanism since maximum energy is imparted to thelinks and pivots of the mechanism by such an adjustment.

According to another method, the reset motion of the breaker handlebetween the OFF and RESET positions is utilized to provide the worknecessary to reset or reseat the solenoid plunger. While this is morepractical in some breakers than others, it also requires accurate partsand fine controls and further requires interphase mechanicalconnections. Additionally, electrical reset schemes have been tried withor without switching but these techniques have also encountereddifficulty for various reasons.

Accordingly, it is an object of the present invention to provide a newand improved electric circuit breaker having an undervoltage trippingdevice that prevents resetting or reseating of the undervoltage releasewhile the undervoltage condition persists. Included in this object isthe provision for a new and improved undervoltage trip control devicethat requires a separate and distinct resetting action not associatedwith the main ONI- OFF handle of the circuit breaker.

Another object of the present invention is to provide a new and improvedelectric circuit breaker of the type described including an undervoltagetrip control device constructed so as to make it impossible to reset thetrip latch of the circuit breaker while the solenoid is in a low voltageor de-energized condition.

Still, anotherobject of the present invention is to provide anundervoltage trip control device that requires the operator of thebreaker to supply a separate resetting force while at the same timepreventing any attempts to defeat the undervoltage release function ofthe unit.

A further object of the present invention is to provide a new andimproved circuit breaker of the type described including an undervoltagetrip control device that has no interphase mechanical connections yetpermits tripping of the breaker from the ON or OFF positions with thesolenoid energized.

A still further object of the present invention is to provide a new andimproved electric circuit breaker and undervoltage trip control deviceof the type described that indicates a breaker tripping condition bymeans of a separate button position.

Still another object of the present invention is to provide a new andimproved electric circuit breaker and undervoltage trip control deviceof the type described which is compact, efficient, simple and relativelytrouble free.

Other objects will be in part obvious and in part pointed out in moredetail hereinafter.

These and related objects are accomplished in accordance with thepresent invention by providing an electric circuit breaker of the typedescribed having a casing, a handle extending through the casing formanually opening and closing the circuit controlled by the circuitbreaker, a trip unit in the casing operable to effect automatic openingof the circuits and a trip control unit adjacent the trip unit forcontrolling the tripping operation of the trip unit. The trip controlunit includes a tripping member movable toward a tripping position fortripping the trip unit. An automatic trip actuator is movable between anelectrically responsive seated position and a released position and isoperable upon movement toward its released position to cause movement ofthe tripping member toward its tripping position. The actuator in itsreleased position is operative to prevent movement of the trippingmember out of its tripping position. A manual reset operator extendsthrough the casing independent of the handle and is movable between arest position and an operating position and is operative upon movementtoward said operating position to urge the tripping member toward itstripping position and the actuator towards its seated position. v

A better understanding of the invention will be obtained from thefollowing detailed description and the accompanying drawings which setforth an illustrative embodiment indicative of the way in which theprinciples of the invention are employed.

A BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a side elevation view partially broken away and partially insection of a molded case circuit breaker incorporating the undervoltagerelease device of the present invention;

FIG 2 is a partial top view of the circuit breaker of FIG. 1 showing thelocation of the independent reset button for manual actuation of therelease device;

FIG. 3 is an enlarged top view of the undervoltage release device of thepresent invention;

FIG. 4 is a side view of the undervoltage release device of FIG. 3showing the device during normal closed circuit operation of thebreaker;

FIG. 5 is a view similar to FIG. 4 showing'the undervoltage trip controldevice in its fully tripped condition.

in response to a low voltage or no voltage condition; and

FIG. 6 is a view similar to FIG. 4 showing the undervoltage trip controldevice upon manual actuation of the device's reset button.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawing ingreater detail wherein like reference numerals indicate like partsthroughout the several figures, the invention is shown as incorporatedin an electric circuit breaker including a generally rectangularinsulating case comprised of a base portion 10 and a cover portion 12.The particular circuit breaker illustrated is a three pole circuitbreaker and comprises three elongated chambers or current paths each ofwhich contain separable contacts (not shown) of a conventional type. Theoperating mechanism which controls movement of the separable contactsbetween open and closed circuit positions is controlled by a manuallyoperated handle 14 projecting centrally from the top of cover 12 formovement between its ON and OFF positions. The operating mechanismincludes a trip unit 16 such as that described and illustrated in U.S.Pat. No. 3,162,740, the disclosure of which is incorporated herein byreference, and a normally restrained but releasable member (not shown)which is adapted to be releasably held by a trip bar 18 housed withinunit 16. The bar 18 extends fully across the circuit breaker and ismounted for pivotal movement between a latched position and a trippedposition where it effects simultaneous opening of all three currentpaths controlled by the circuit breaker.

For the purpose of initiating a tripping operation of the trip unit uponthe occurence of a predetermined decrease in voltage in a selectedcircuit controlled by the breaker, an undervoltage trip control deviceis provided as indicated generally in FIG. 1 by the numeral 20. Theundervoltage release device 20 is enclosed within the casing and isoperatively associated with a reset button 22 that projects upwardlythrough an aperture 24 in the casing cover 12 intermediate the manualhandle 14 and the side of the casing. In the embodiment illustrated theprotruding portion of button 22 is enclosed by a deformable dust cap 26attached to a cylindrical sleeve or guide 28 secured to the cover 12 atthe aperture 24.

Referring now to FIGS. 36, the undervoltage trip control or releasedevice is shown as comprised of a generally flat sheet metal supportingframe having a central planar portion 30 with an enlarged circularaperture 32 adjacent one end thereof for registry with the reset buttonaperture 24 in the cover of the circuit breakers casing. The supportincludes front and rear end walls 34, 36 respectively that are bent inopposite directions at approximately 90 to the central planar portion 30and provide appropriate means for mounting the entire undervoltage tripcontrol unit within the circuit breaker. In this connection, the frontbent-up end wall 34 is preferably mounted on the trip unit 16 of thecircuit breaker and secured thereto by means of a suitable threadedconnector 38. Side flanges 42, 44

depend downwardly from the central planar portion 30 of the support andprovide means for mounting the movable components of the trip controlunit.

A tripping lever 46 is pivotally mounted on the depending side flange 42adjacent the upstanding front wall 34 by means of fixed pin 48 and inturn is pivotally connected by pin 50 to a flat sheet metal slide member52. In the embodiment illustrated the member 52 is provided with anelongated tripping plunger portion 54 adapted to extend into the tripunit 16 for tripping contact with the trip bar 18. As best shown inFIGS. 46, the tripping lever 46 is a generally triangular member withthe aforementioned pivotal connections at two of its three corners andthe free corner 56 thereof positioned remotely from front wall 34 insuch a manner that pivotal movement of the tripping lever 46 about thefixed pivot pin 48 in a counterclockwise direction as viewed in FIG. 4will drive the slide member 52 to the left as viewed in FIG. 4 so as tobring the plunger portion 52 into engagement with the trip bar 18. Asshown, the slide member 52 is also provided with a linear elongated slotor guideway 58 within which is positioned a laterally extending guidetab 60 located generally within the plane of the main body portion 30 ofthe support and extending laterally therefrom. In this man ner, theslide 52 is restrained to travel along a reciprocally linear path duringmovement between its retracted and advanced positions in response to thepivotal movement of the tripping lever 46.

A solenoid 62 is positioned in operative alignment with the elongatedslide member 52 and is rigidly mounted on the support adjacent the reardepending wall 36 by threaded connectors 64. The solenoid is providedwith a generally cylindrical plunger 66 fixedly mounting a flat guideplate 68 on its free end for restrainably confining a plunger drivespring 70 coiled around the plunger between the plate 68 and thesolenoid 62. The guide plate 68 is provided with topand bottom notches72 and the reciprocating slide member 52 is provided with an enlargedrecess 74 adjacent its rearward end and above guideway 58 so that theslide 52 and the plate 68 on the solenoid plunger interfit for relativesliding movement while cooperating to provide coaxial alignmenttherebetween.

A tripping plunger return spring 76 is connected at one end to the guideplate 68 and at its opposite end to the pivot pin 50 interconnecting theguide plate 68 with the slide member 52. Thus, as will be appreciated,the slide member and the solenoid plunger may move independently or inunison between their respective extended or retracted positions.However, when the solenoid plunger is in its retracted or seatedposition and the slide member is in its extended or tripping position,the tripping plunger return spring 76 will be in its extended or loadedcondition. Accordingly, unless the slide 52 is restrained, the returnspring 76 will bias the slide toward the solenoid plunger after thelatter has moved to its seated position. Therefore, as the solenoidplunger is moved under the influence of its drive spring 70 out of itsseated position toward its extended position, the guide plate 68 willdrivably move the slide member 52 to the left as viewed in FIG. 4 towardits extended or tripping position shown in FIG. 5.

Also pivotably mounted on the support is the mechanism employed inresetting or reseating the solenoid plunger 66 after it has beenreleased by an undervoltage condition. As mentionedhereinbefore, theresetting mechanism includes a reset button 22 extending through a resetaperture 24 in the cover 12 of the casing intermediate the manual ON/OFFlever 14 and side wall of the casing. The aperture 24 in the cover ispreferably provided with a tubular guideway 28 supportably mounted onthe cover 12 and enclosed by a resilient dust cover or cap 26 thatlockably interfits over the tubular guideway 28. The reset button 22 ofrod-like construction is slideably mounted within the guide 28 andextends into the interior of the circuit breaker so as to pass throughthe circular opening 32 in the central planar portion 30 of the supportfor the undervoltage trip device.

The reset mechanism of the trip control device includes a sheet metalaccelerator plate 80 pivotably mounted on a pin 82 extending between thedepending flanges 42, 44 of the support so that the free end of theplate underlies the aperture 32 and is engaged by the reset button 22. Aflat sheet metal resetting lever 84 is also mounted on the pin 82 forpivotable movement and includes a first uppermost leg portion 86 whichextends upwardly from the pin 82 for engagement by its free end with theguide plate 68. A second leg portion 88 of the resetting lever 84extends downwardly at an angle slightly greater than 90 relative to thefirst leg portion and is pivotably connected by pin 90 at its end to aspaced actuating lever 92 having an elongated slot 94 therein throughwhich passes the mounting pin 82. The flat sheet actuator lever 92 isdisposed so as to be contacted by the free end of the accelerator plate80 at the end 96 of the actuator remote from the elongated slot 94. Theopposite end of the actuator lever, that is, the end adjacent theelongated slot 94 and remote from the pin 90 is provided with a drivedog 98 adapted to contact the free corner 56 of the triangular trippinglever 46 to effect counterclockwise pivotable movement of the trippinglever toward its tripping position.

In FIG. 4 the parts are shown in the positions which they occupy duringnormal operation of the circuit breaker. In this condition the solenoidplunger 66 is held in its retracted or seated position within thesolenoid 62 while it is energized by the operating referenced voltage.The slide member 52 and its associated elongated tripping plungerportion 54 is held in its retracted position by the biasing action ofthe trip return spring 76 and the tripping lever 46 is positioned sothat the free corner 56 thereof bears against the dog 98 of theactuating lever 92. Additionally in this condition the reset button 22rests on accelerator plate 80 and tends to hold the leg 86 of resetlever 84 against guide plate 68.

If the voltage applied to the solenoid decreases a predetermined amount,such as to a level of about 60 percent of its referenced voltage, theplunger 66 will fall out, that is, will be driven outwardly from itsseated position by the driving action of thedrive spring 70. The guideplate 68 will bear against the coaxially aligned slide member 52,driving the member 52 to the left as viewed in FIG. 4 and simultaneouslyrotating the tripping lever 46 counterclockwise as viewed in FIG. 4causing the tripping plunger 54 to operate against the trip bar 18and'effect tripping of the circuit breaker. At the same time, the guideplate 68 drives the arm 86 of the reset lever 84 counterclockwise asviewed in FIG. 4 about its fixed pivot pin 82. The simultaneous pivotalmovement of the tripping lever 46 and reset lever 84 elevates theactuator lever 92 as well as the accelerator plate 80 and reset button22. As a result, the undervoltage trip control device 20 assumes theposition shown in FIG. 5 when the circuit breaker is in its tripcondition and the reset button indicates the tripped condition by itselevated position. Since the solenoid plunger drive spring will continueto urge the tripping plunger 54 toward its tripped position until theplunger 66 is reseated, movement of the manually operated handle 14between its ON and OFF positions will be ineffective to close thecontacts of the circuit breaker. Thus the operator is required toperform the positive act of pushing the reset button in order to resetor reseat the plunger prior to turning the manual handle 14 of thecircuit breaker to its ON position.

The separate and distinct reset action required in the circuit breakerof the present invention can be effected by depressing the reset button22 to drive the accelerator plate clockwise about its pivot pin 82thereby simultaneously driving the free end 96 of the actuating lever 92downwardly or clockwise as viewed in FIG. 5. As will be appreciated, thedog 98 on the end of the actuating lever 92 firmly engages the freecorner 56 of the tripping lever 46 to assure that the tripping plunger54 is held in its tripping position during the resetting operation.Additionally, the clockwise movement of the actuator lever 92 willimpart clockwise movement to the resetting lever 84 causing theuppermost leg 86 thereof to bear against the guide plate 68 driving itrearwardly against the bias of its drive spring 70 toward its seatedposition. This will also load the slide member return spring 76 sincethe dog end 98 of the actuator lever 92 will continue to retain thetripping plunger 54 and pin 50 in their tripped position.

So long as the undervoltage condition persists, the solenoid will beineffective in retaining the plunger 66 in its seated position andrelease of the reset button 22 will permit the plunger drive spring 70to drivably return the plunger to its extended position. Once theundervoltage condition is corrected, the trip control unit 20 can bereset by depressing the reset button 22 to drive the plunger to itsreset or reseated position and load the tripping plunger return spring76. This condition of the device is shown in FIG. 6.

The correction of the undervoltage condition permits the solenoid toretain the plunger in its seated position so that the release of thereset button 22 permits clockwise movement of the tripping lever 46 asthe slide member 52 is drawn to the right as viewed in FIG. 6 under thedriving action of theloaded tripping plunger return spring 76. Thewithdrawal of the tripping plunger 54 will permit resetting of the tripbar 18 thereby enabling the operator to manually operate the ON/OFFhandle 14 to the ON position.

It is an advantageous feature of the present invention that the separatereset button described herein will permit tripping of the circuitbreaker from either an ON or OFF position with the solenoid energized.Thus, if the undervoltage trip control device is in the position shownin FIG.4 with the solenoid in an energized condition and the plunger 66held in its seated position, an operator may trip the circuit breaker bysimply depressing the reset button 22. Since the reset lever 84 isrestrained against clockwise movement by the contact of its upper leg 86with the guide plate 68, the actuator lever 92 will pivot about thepivotal connection so that the dog end 98 of the'actuator lever maytravel clockwise bearing against the free corner 56 of the trippinglever 46 to move the tripping lever counterclockwise against the bias ofthe tripping plunger return spring 76. This in turn will drive the slidemember 52 to the left as viewed in FIG. 4 until it reaches its trippingposition and the mechanism assumes the position shown in FIG. 6. In thisconnection it will be noted that this positioning of the parts of thedevice is substantially the same as during the resetting operation.Thereafter, release of the reset button 22 will permit the slide memberreturn spring 76 to return the tripping plunger 54 to its retractedposition in substantially the same manner as it returns after aresetting operation.

As can be seen from the foregoing detailed description the undervoltagerelease device of the present invention advantageously preventsresetting of the device while an undervoltage condition persists orwhile the solenoid actuator is in a de-energized condition.Additionally, the device requires a separate and distinct resettingaction not associated with the main ON/OFF handle of the circuitbreaker, requiring the operator of the breaker to supply a saidindependent resetting force thereto. At the same time the independentundervoltage tripping device of the present invention prevents anyattempt to defeat the undervoltage release function of the unit. Anadded feature of the device is its ability to permit the operator totrip the circuit breaker from an ON or OFF position with the solenoidenergized and further permits an operator familiar with the device todetect a breaker trip condition by means of the position of the resetbutton. Further, as is evident from the drawing and description, all ofthese advantages are achieved within a device that is compact,efficient, simple and relatively trouble free.

As will be apparent to persons skilled in the art, variousmodifications, adaptations and variations of the foregoing specificdisclosure can be made without departing from the teachings of thepresent invention.

I claim: 7

1. An electric circuit breaker comprising a casing, a handle extendingthrough the casing for manually opening and closing the circuitscontrolled by the circuit breaker, a trip unit in the casing operable toeffect automatic opening of said circuits, a trip control unit adjacentthe trip unit for controlling the tripping operation of the trip unitincluding a tripping member movable toward a tripping position fortripping the trip unit, an automatic trip actuator movable between anelectrically responsive seated position and a released position andoperable upon movement toward its released position to cause movement ofthe tripping member toward its tripping position, said trip actuator inits released position being operative to prevent movement of thetripping member out of its tripping position, and a reset operatorindependent of the handle and movable between a reset position and anoperating position and operative upon movement toward said operatingposition to urge the tripping member toward its tripping position andthe actuator toward its seated position.

2. The circuit breaker of claim 1 wherein the trip control unit includesa solenoid operative upon energization to a predetermined level toretain the trip actuator in its seated position and actuator drive meanseffective upon a predetermined reduction in the level of saidenergization to drive the actuator out of its seated position toward itsreleased position to trip the circuit breaker.

3. The circuit breaker of claim 1 wherein the reset operator includes areset button operative upon actuation to prevent movement of thetripping member out of its tripping position and to drive the tripactuator into its seated position to effect resetting of the tripcontrol unit.

4. The circuit breaker of claim 1 wherein the reset operator includes areset button operative upon actuation to drive the tripping membertoward its tripping position while the trip actuator is in its seatedposition.

5. The circuit breaker of claim 1 including actuator drive meansoperative on the trip actuator for driving the actuator toward itsreleased position and tripping member drive means interconnecting thetripping member and the actuator for driving the tripping member out ofits tripping position toward a retracted position upon movement of theactuator to its seated position.

6. The circuit breaker of claim I including a reset lever operativelyconnected with the reset operator and responsive to movement of the tripactuator toward its released position to change the position of thereset operator for indicating the tripped condition of the circuitbreaker.

7. The circuit breaker of claim 1 including a reset lever in drivingengagement with the trip actuator, an actuating lever interconnectingthe reset operator with the reset lever' and the tripping member, andspring means biasing the tripping member toward the trip actuator, saidactuating lever being operative to restrain movement of the trippingmember out of its tripping position upon movement of the reset operatortoward its operating position and to impart a driving force to the resetlever to cause the reset lever to drive the trip actuator toward itsseated position against the bias of said spring means to effectresetting of the trip control unit.

8. The circuit breaker of claim 1 wherein the tripping member is inaxial alignment with the trip actuator and is operable between atripping position and a retracted position, said actuator beingoperative during movement toward its released position to drivablyengage said tripping member and drive said member toward its trippingposition, said unit including a tripping lever connected to saidtripping member for driving said member toward its tripping positionindependently of said actuator.

9. The circuit breaker of claim 8 including an actuating leveroperatively interconnecting the reset operator and the tripping leverfor driving the tripping lever to effect tripping upon movement of thereset operator to its operating position.

10. The circuit breaker of claim 1 wherein the reset operator is amanually operated member protruding through the casing at a locationspaced from the handle.

11. For use with an electric circuit breaker having an ON/OFF handle foropening and closing the circuits controlled by the circuit breaker and atrip unit for effecting automatic opening of said circuits, anelectrically responsive trip control unit for controlling the trippingoperation of the trip unit including a tripping member movable toward atripping position for tripping the trip unit, an automatic trip actuatorincluding a plunger movable between an electrically responsive seatedposition and a released position and operable upon movement toward itsreleased position to cause movement of the tripping member toward itstripping position, said plunger in its released position being operativeto prevent movement of the tripping'member out of its tripping position,and a reset operator independent of the handle and movable between areset position and an operating position and operative upon movementtoward said operating position to urge the tripping member toward itstripping position and the plunger toward its seated position.

12. The trip control unit of claim 11 wherein the automatic tripactuator includes drive means for driving the plunger toward itsreleased position, and a solenoid operative on said plunger forretaining said plunger in its seated position against the driving actionof said drive means, said solenoid being ineffective in retaining saidplunger upon the occurrence of a predetermined drop in the voltageapplied to the solenoid.

13. The trip control unit of claim 11 including a reset leveroperatively connecting the plunger and the reset operator and a plungerdrive spring for driving the plunger toward its released position, saidreset lever being responsive to movement of the reset operator towardits operating position to drive the plunger toward its seated positionagainst the bias of the plunger drive spring for resetting the tripcontrol unit.

14. The trip control unit of claim 11 including a tripping leverconnected to the tripping member for movement therewith, an actuatinglever drivably connecting the tripping lever and the reset operator anda tripping member return spring biasing the tripping member toward theplunger, said actuating lever being responsive to movement of the resetoperator toward its operating position to drive the tripping lever andtripping member away from the plunger against the bias of said returnspring.

15. The trip control unit of claim 11 wherein the reset operator is amanually operated button accessable from the exterior of the circuitbreaker and spaced from the ON/OFF handle.

1. An electric circuit breaker comprising a casing, a handle extendingthrough the casing for manually opening and closing the circuitscontrolled by the circUit breaker, a trip unit in the casing operable toeffect automatic opening of said circuits, a trip control unit adjacentthe trip unit for controlling the tripping operation of the trip unitincluding a tripping member movable toward a tripping position fortripping the trip unit, an automatic trip actuator movable between anelectrically responsive seated position and a released position andoperable upon movement toward its released position to cause movement ofthe tripping member toward its tripping position, said trip actuator inits released position being operative to prevent movement of thetripping member out of its tripping position, and a reset operatorindependent of the handle and movable between a reset position and anoperating position and operative upon movement toward said operatingposition to urge the tripping member toward its tripping position andthe actuator toward its seated position.
 2. The circuit breaker of claim1 wherein the trip control unit includes a solenoid operative uponenergization to a predetermined level to retain the trip actuator in itsseated position and actuator drive means effective upon a predeterminedreduction in the level of said energization to drive the actuator out ofits seated position toward its released position to trip the circuitbreaker.
 3. The circuit breaker of claim 1 wherein the reset operatorincludes a reset button operative upon actuation to prevent movement ofthe tripping member out of its tripping position and to drive the tripactuator into its seated position to effect resetting of the tripcontrol unit.
 4. The circuit breaker of claim 1 wherein the resetoperator includes a reset button operative upon actuation to drive thetripping member toward its tripping position while the trip actuator isin its seated position.
 5. The circuit breaker of claim 1 includingactuator drive means operative on the trip actuator for driving theactuator toward its released position and tripping member drive meansinterconnecting the tripping member and the actuator for driving thetripping member out of its tripping position toward a retracted positionupon movement of the actuator to its seated position.
 6. The circuitbreaker of claim 1 including a reset lever operatively connected withthe reset operator and responsive to movement of the trip actuatortoward its released position to change the position of the resetoperator for indicating the tripped condition of the circuit breaker. 7.The circuit breaker of claim 1 including a reset lever in drivingengagement with the trip actuator, an actuating lever interconnectingthe reset operator with the reset lever and the tripping member, andspring means biasing the tripping member toward the trip actuator, saidactuating lever being operative to restrain movement of the trippingmember out of its tripping position upon movement of the reset operatortoward its operating position and to impart a driving force to the resetlever to cause the reset lever to drive the trip actuator toward itsseated position against the bias of said spring means to effectresetting of the trip control unit.
 8. The circuit breaker of claim 1wherein the tripping member is in axial alignment with the trip actuatorand is operable between a tripping position and a retracted position,said actuator being operative during movement toward its releasedposition to drivably engage said tripping member and drive said membertoward its tripping position, said unit including a tripping leverconnected to said tripping member for driving said member toward itstripping position independently of said actuator.
 9. The circuit breakerof claim 8 including an actuating lever operatively interconnecting thereset operator and the tripping lever for driving the tripping lever toeffect tripping upon movement of the reset operator to its operatingposition.
 10. The circuit breaker of claim 1 wherein the reset operatoris a manually operated member protruding through the casing at alocatIon spaced from the handle.
 11. For use with an electric circuitbreaker having an ON/OFF handle for opening and closing the circuitscontrolled by the circuit breaker and a trip unit for effectingautomatic opening of said circuits, an electrically responsive tripcontrol unit for controlling the tripping operation of the trip unitincluding a tripping member movable toward a tripping position fortripping the trip unit, an automatic trip actuator including a plungermovable between an electrically responsive seated position and areleased position and operable upon movement toward its releasedposition to cause movement of the tripping member toward its trippingposition, said plunger in its released position being operative toprevent movement of the tripping member out of its tripping position,and a reset operator independent of the handle and movable between areset position and an operating position and operative upon movementtoward said operating position to urge the tripping member toward itstripping position and the plunger toward its seated position.
 12. Thetrip control unit of claim 11 wherein the automatic trip actuatorincludes drive means for driving the plunger toward its releasedposition, and a solenoid operative on said plunger for retaining saidplunger in its seated position against the driving action of said drivemeans, said solenoid being ineffective in retaining said plunger uponthe occurrence of a predetermined drop in the voltage applied to thesolenoid.
 13. The trip control unit of claim 11 including a reset leveroperatively connecting the plunger and the reset operator and a plungerdrive spring for driving the plunger toward its released position, saidreset lever being responsive to movement of the reset operator towardits operating position to drive the plunger toward its seated positionagainst the bias of the plunger drive spring for resetting the tripcontrol unit.
 14. The trip control unit of claim 11 including a trippinglever connected to the tripping member for movement therewith, anactuating lever drivably connecting the tripping lever and the resetoperator and a tripping member return spring biasing the tripping membertoward the plunger, said actuating lever being responsive to movement ofthe reset operator toward its operating position to drive the trippinglever and tripping member away from the plunger against the bias of saidreturn spring.
 15. The trip control unit of claim 11 wherein the resetoperator is a manually operated button accessable from the exterior ofthe circuit breaker and spaced from the ON/OFF handle.